SIST-TS CEN/TS 17390-2:2020

SLOVENSKI STANDARD
01-marec-2020
Molekularne diagnostične preiskave in vitro - Specifikacije za predpreiskovalne
procese za cirkulirajoče tumorske celice (CTC) v venski polni krvi - 2. del: Izolirana
DNK
Molecular in vitro diagnostic examinations - Specifications for pre-examination processes
for circulating tumor cells (CTCs) in venous whole blood - Part 2: Isolated DNA
Molekularanalytische in vitro-diagnostische Verfahren - Spezifikationen für
präanalytische Prozesse für zirkulierende Tumorzellen (CTC) in venösen Vollblutproben
- Teil 2: Isolierte DNA
Analyses de diagnostic moléculaire in vitro - Spécifications relatives aux processus
préanalytiques pour les cellules tumorales circulantes (CTCs) dans le sang total veineux
- Partie 2: ADN extrait
Ta slovenski standard je istoveten z: CEN/TS 17390-2:2020
ICS:
11.100.10 Diagnostični preskusni In vitro diagnostic test
sistemi in vitro systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TS 17390-2
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
January 2020
TECHNISCHE SPEZIFIKATION
ICS 11.100.10
English Version
Molecular in vitro diagnostic examinations - Specifications
for pre-examination processes for circulating tumor cells
(CTCs) in venous whole blood - Part 2: Isolated DNA
Analyses de diagnostic moléculaire in vitro - Molekularanalytische in vitro-diagnostische Verfahren
Spécifications relatives aux processus préanalytiques - Spezifikationen für präanalytische Prozesse für
pour les cellules tumorales circulantes (CTCs) dans le zirkulierende Tumorzellen (CTC) in venösen
sang total veineux - Partie 2: ADN extrait Vollblutproben - Teil 2: Isolierte DNA
This Technical Specification (CEN/TS) was approved by CEN on 27 October 2019 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 17390-2:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 General considerations . 10
5 Outside the laboratory . 10
5.1 Specimen collection . 10
5.2 Transport requirements. 12
6 Inside the laboratory . 13
6.1 Specimen reception . 13
6.2 Storage requirements for the venous whole blood specimen . 13
6.3 Enrichment of CTCs . 13
6.4 Quality of enriched CTCs. 14
6.5 Storage of enriched CTCs . 14
6.6 Isolation of the CTCs . 15
6.7 Processing of isolated CTCs . 16
6.8 Isolation of DNA from an enriched CTC sample . 16
6.9 Quantity and quality assessment of isolated DNA from enriched or isolated CTCs . 17
6.10 Storage of isolated DNA from enriched CTCs . 17
Annex A (informative) Exemplary complete workflow for the molecular characterization of
single CTCs . 19
Annex B (informative) Decision guideline for critical steps of the CTC pre-analytical
workflow for DNA isolation . 22
Bibliography . 26

European foreword
This document (CEN/TS 17390-2:2020) has been prepared by Technical Committee CEN/TC 140 “In
vitro diagnostic medical devices”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
CEN/TS 17390 consists of the following parts, under the general title Molecular in vitro diagnostic
examinations — Specifications for pre-examination processes for Circulating Tumor Cells (CTCs) in venous
whole blood:
— Part 1: Isolated RNA
— Part 2: Isolated DNA
— Part 3: Preparations for analytical CTC staining
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Introduction
Solid tumours release cells and bioanalytes into blood and other body fluids. This has opened the option
of minimally-invasive tumour detection, diagnosis and characterization from venous whole blood
(liquid biopsies). Liquid biopsies are expected to enable earlier detection and diagnosis of cancers and
advance personalized patient treatment. These applications have become one of the fastest growing
segments of the entire diagnostic market.
Circulating tumour cells (CTCs) in venous whole blood reflect the disease complexity that evolves
during tumour progression, with distinct genetic, epigenetic and expression features. Beside the
prognostic role of CTC identification and/or enumeration in cancer progression, CTC molecular
characterization can improve e.g. disease outcome prediction, therapeutic guidance and post-treatment
monitoring of the patient.
CTCs are now considered as a surrogate of tumour tissue in cancer early development, progression and
metastatic phase.
Molecular characterization of CTCs can provide for example a strategy for monitoring cancer genotype
during systemic therapies [1], identification of mechanisms of disease progression, identification of
novel targets for biological treatment [2] and to select targeted therapies. Moreover, CTC single-cell
sequencing is as an important tool for tumour genomic heterogeneity analysis [3] [4] [5]. Molecular
examination techniques such as qPCR, dPCR and sequencing methods including next generation
sequencing (NGS) enable to characterize CTC specific DNA features.
CTCs are fragile and tend to degrade within a few hours when collected in conventional blood collection
tubes, e.g. EDTA containing tubes, without dedicated CTC stabilizers. CTCs are extremely rare, especially
in early disease, e.g. less than 10 cells per 10 ml of blood, representing a ratio of approx. 1:10 CTCs to
white blood cells (WBCs). This low ratio represents a significant challenge to CTC enrichment required
for examination. Furthermore, co-enrichment of normal blood cells causes a dilution of CTCs. The
challenge is to minimize the amount of co-enriched WBCs for subsequent accurate and sensitive
detection of CTC specific genetic and epigenetic alterations, especially when dealing with minor tumour
cell clones.
Special measures need to be taken to get rid of the WBCs in order to obtain good quality DNA samples
characterized by high purity and thus representative of the mutational pattern within the tumour.
Standardization of all steps of the pre-examination process is required. This includes blood collection
and stabilization, transport, storage, CTC enrichment, CTC isolation (if required), and DNA isolation. An
exemplary complete workflow for the molecular characterization of single CTCs is provided in Annex A.
A decision guideline for the critical steps of the CTC pre-analytical workflow for DNA isolation is
provided in Annex B.
This document describes special measures that need to be taken to obtain appropriate quality and
quantity of DNA from CTC containing blood specimens for subsequent examination.
In this document, the following verbal forms are used:
— “shall” indicates a requirement;
— “should” indicates a recommendation;
— “may” indicates a permission;
— “can” indicates a possibility or a capability.
1 Scope
This document gives guidelines on the handling, storage, processing and documentation of venous
whole blood specimens intended for the examination of human DNA isolated from circulating tumour
cells (CTCs) during the pre-examination phase before a molecular examination is performed.
This document is applicable to molecular in vitro diagnostic examinations including laboratory
developed tests performed by medical laboratories. It is also intended to be used by laboratory
customers, in vitro diagnostics developers and manufacturers, biobanks, institutions and commercial
organizations performing biomedical research, and regulatory authorities.
This document does not cover the isolation of genomic DNA directly from venous whole blood
containing CTCs. This is covered in EN ISO 20186-2, Molecular in vitro diagnostic examinations -
Specifications for pre-examination processes for venous whole blood - Part 2: Isolated genomic DNA.
This document does not cover the isolation of specific white blood cells and subsequent isolation of
genomic DNA therefrom.
This document does not cover pre-analytical workflow requirements for viable CTC cryopreservation
and culturing.
NOTE 1 The requirements given in this document can also be applied to other circulating rare cells (e.g. foetal
cells).
NOTE 2 International, national or regional regulations or requirements can also apply to specific topics
covered in this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 15189:2012, Medical laboratories - Requirements for quality and competence (ISO 15189:2012,
Corrected version 2014-08-15)
ISO 15190, Medical laboratories — Requirements for safety
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 15189 and the following
terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
aliquot
portion of a larger amount of homogenous material, assumed to be taken with negligible sampling error
Note 1 to entry: The term is usually applied to fluids. Tissues are heterogeneous and therefore cannot be
aliquoted.
Note 2 to entry: The definition is derived from References [6], [7] and [8].
[SOURCE: EN ISO 20166-3:2019, 3.1]
3.2
ambient temperature
unregulated temperature of the surrounding air
[SOURCE: EN ISO 20166-3:2019, 3.2]
3.3
analyte
component represented in the name of a measurable quantity
[SOURCE: EN ISO 17511:2003, 3.2, modified — EXAMPLE has been removed.]
3.4
analytical test performance
accuracy, precision, specificity and sensitivity of a test to measure the analyte of interest
Note 1 to entry: Other test performance characteristics such as robustness, repeatability can apply as well.
[SOURCE: EN ISO 20184-1:2018, 3.4, modified — “specificity” was added.]
3.5
blood collection set
intravenous device specialized for venipuncture consisting of a stainless steel bevelled needle and tube
(tubing) with attached plastic wings and fitting connector
Note 1 to entry: The connector attaches to an additional blood collection device, e.g. a blood collection tube.
3.6
blood collection tube
tube used for blood collection, usually in a vacuum which forces blood from the vein through the needle
and into the tube
3.7
backflow
flow of a liquid opposite to the usual or desired direction
3.8
circulating tumor cells
CTCs
cells present in blood, originating from a primary and/or metastatic site of a tumor
3.9
CTC enrichment
any method that is able to increase the ratio of CTCs to other cells
3.10
CTC isolation
any method resulting in a sample containing CTCs without any other cell type
3.11
DNA
deoxyribonucleic acid
polymer of deoxyribonucleotides occurring in a double-stranded (dsDNA) or single-stranded (ssDNA)
form
[SOURCE: EN ISO 22174:2005, 3.1.2]
3.12
diagnosis
identification of a disease from its signs and symptoms
Note 1 to entry: Where the diagnostic process can involve examinations and tests for classification of an
individual's condition into separate and distinct categories or subclasses that allow medical decisions about
treatment and prognosis to be made
[SOURCE: EN ISO 20184-1:2018, 3.6]
3.13
examination
analytical test
set of operations having the object of determining the value or characteristics of a property
Note 1 to entry: Processes that start with the isolated analyte and include all kinds of parameter testing or
chemical manipulation for quantitative or qualitative examination.
[SOURCE: EN ISO 15189:2012, 3.7, modified — Notes to entry 1 to 3 have been removed, Note 1 to
entry has been added and “analytical test” has been added as a preferred term.]
3.14
examination performance
analytical test performance
analytical performance
ability of an examination procedure to measure or detect a particular analyte
Note 1 to entry: Analytical performance is determined from analytical performance studies used to assess the
ability of an in vitro diagnostic examination procedure to measure or detect a particular analyte.
Note 2 to entry: Analytical performance includes such characteristics as analytical sensitivity, detection limit,
analytical specificity (interference and cross-reactivity), trueness, precision and linearity.
[SOURCE: ISO/TS 17822-1:2014, 3.2, modified — “analytical test performance” and “analytical
performance” have been added as preferred terms.]
3.15
examination manufacturer
analytical test manufacturer
group or company that provides the specific analytical test
3.16
needle holder
barrel used in routine venipuncture procedures to hold the blood collection tube in place and to protect
the phlebotomist from direct contact with blood
[SOURCE: EN ISO 20186-1:2019, 3.24]
3.17
pre-examination processes
preanalytical phase
preanalytical workflow
processes that start, in chronological order, from the clinician’s request and include the examination
request, preparation and identification of the patient, collection of the primary sample(s),
transportation to and within the medical or pathology laboratory, CTC enrichment, CTC isolation where
applicable, isolation of analytes, and end when the analytical examination begins
Note 1 to entry: The pre-examination phase includes preparative processes that influence the outcome of the
intended examination.
[SOURCE: EN ISO 15189:2012, 3.15, modified — “pre-analytical workflow” has been added as a
preferred term, Note 1 to entry has been added and the definition has been extended.]
3.18
primary sample
specimen
discrete portion of a body fluid, breath, hair or tissue taken for examination, study or analysis of one or
more quantities or properties assumed to apply for the whole
[SOURCE: EN ISO 15189:2012, 3.16, modified — Notes to entry 1 to 3 have been removed.]
3.19
proficiency testing
evaluation of participant performance against pre-established criteria by means of inter-laboratory
comparisons
[SOURCE: EN ISO/IEC 17043:2010, 3.7, modified — Notes to entry 1 to 3 have been removed.]
3.20
DNA proficiency testing program
proficiency testing for DNA based examinations
3.21
room temperature
for the purposes of this document, temperature in the range of 18 °C to 25 °C
Note 1 to entry: Local or national regulations can have different definitions.
3.22
sample
one or more parts taken from a primary sample
[SOURCE: EN ISO 15189:2012, 3.24, modified — EXAMPLE has been removed.]
3.23
stability
ability of a sample material, when stored under specified conditions, to maintain a stated property value
within specified limits for a specified period of time
Note 1 to entry: The analyte for the purpose of this document is DNA.
[SOURCE: ISO Guide 30:2015, 2.1.15, modified — The words “reference material” were replaced by
“sample material”.]
3.24
storage
prolonged interruption of the preanalytical workflow of a sample or analyte respectively, or of their
derivatives e.g., stained sections or tissue blocks, under appropriate conditions in order to preserve
their properties
Note 1 to entry: Long-term storage typically occurs in laboratory archives or in biobanks.
[SOURCE: EN ISO 20166-3:2019, 3.24]
3.25
validation
confirmation, throughout the provision of objective evidence, that the requirements for a specific
intended use or application have been fulfilled
Note 1 to entry: The term “validated” is used to designate the corresponding status.
[SOURCE: EN ISO 9000:2015, 3.8.13, modified — Notes to entry 1 to 3 have been removed.]
3.26
verification
confirmation, through provision of objective evidence, that specified requirements have been fulfilled
Note 1 to entry: The term “verified” is used to designate the corresponding status.
Note 2 to entry: Confirmation can comprise activities such as:
— performing alternative calculations,
— comparing a new design specification with a similar proven design specification,
— undertaking tests and demonstrations, and
— reviewing documents prior to issue.
[SOURCE: EN ISO 9000:2015, 3.8.12, modified — Notes to entry 1 and 2 have been removed.]
3.27
workflow
series of activities necessary to complete a task
[SOURCE: EN ISO 20166-3:2019, 3.29]
4 General considerations
For general statements on medical laboratory quality management systems and in particular on
specimen collection and handling (including avoidance of cross contaminations) see
EN ISO 15189:2012, 4.2, 5.4.4, or EN ISO/IEC 17020:2012, 7.2 and 8. The requirements on laboratory
equipment, reagents, and consumables according to EN ISO 15189:2012, 5.3 shall be followed;
EN ISO 15189:2012, 5.5.1.2 and 5.5.1.3 and EN ISO/IEC 17020:2012, 6.2 can also apply.
All steps of a diagnostic workflow can influence the final analytical test result. Thus, the entire workflow
including biomolecule stability and specimen and/or sample storage conditions shall be verified and
validated. Workflow steps which cannot always be controlled shall be documented. A risk assessment of
non-controllable workflow steps including their potential impact on the analytical test performance
shall be performed and mitigation measures shall be established to enable the required analytical test
performance.
CTC analysis usually involves a CTC enrichment step (e.g. by size, immunomagnetic-, or microfluidic-
based approaches) prior to DNA isolation. Depending on the requirements of the examination, enriched
CTCs can undergo additional steps after CTC enrichment such as further characterization and selection
prior to DNA isolation (see 6.4 and 6.6). Due to the nature of the specimen/sample and the complexity
of the procedure potentially affecting the yield, purity and integrity of DNA, appropriate measures shall
be taken during the pre-examination workflow to obtain suitable quantity and quality of DNA derived
from CTCs for the examination.
The degree of contamination of CTCs with WBCs or other cells is critical. The presence of WBCs in a CTC
enriched sample is unavoidable and can strongly affect the performance of the examination e.g. the
sensitivity of detection of a somatic mutation. To overcome this problem, an isolation step can be
necessary to obtain a pure CTC sample for DNA isolation.
Safety regulations on specimen transport and handling shall be considered (see EN ISO 15189:2012,
5.2.3 and 5.4.5 and ISO 15190).
During the whole pre-examination process, precautions shall be taken to avoid cross contamination
between different specimens/samples, e.g. by using single-use material whenever feasible or
appropriate cleaning procedures between processing of different specimens/samples.
If a commercial product is not used in accordance with the manufacturer’s instructions, responsibility
for its use and performance lies with the user.
5 Outside the laboratory
5.1 Specimen collection
5.1.1 Information about the specimen donor/patient
The documentation shall include the ID of the specimen donor/patient, which can be in the form of a
code.
The documentation should include, but is not limited to:
a) the relevant health status of the specimen donor/patient (e.g. healthy, disease type, concomitant
disease, demographics (e.g. age and gender));
b) the information about medical treatment and special treatment prior to blood collection;
c) the type and purpose of the proposed examination requested;
d) the appropriate consent from the specimen donor/patient.
See also EN ISO 15189:2012, 5.4.4.
5.1.2 Selection of the venous whole blood collection tube by the laboratory
Due to the low number of CTCs, a high recovery rate is required during enrichment. This can be
hampered by the potential instability of CTCs during transport and storage, leading to a reduction of the
CTC number in the specimen or reduced compatibility with the enrichment system [9].
Therefore, venous whole blood should be collected in appropriate collection tubes with stabilizers
maintaining the integrity of the CTCs for enabling sensitive DNA examination.
Where the CTC examination manufacturer requires usage of a dedicated blood collection tube, this shall
be used. Where the CTC examination manufacturer does not provide any instructions on blood
collection tube requirements, but the CTC isolation manufacturer does, these shall be used.
Where requirements on selecting a dedicated blood collection tube are neither available from the CTC
examination manufacturer nor from the CTC isolation manufacturer, the CTC enrichment
manufacturer’s instructions shall be followed.
Where instructions are not available, the laboratory shall specify, verify and validate the usage of an
appropriate blood collection tube. This shall include the verification of the blood collection tube’s
compatibility with the intended CTC enrichment, isolation and examination method.
Where the laboratory decides to use a blood collection tube without a CTC stabilizer, the blood
specimen should be processed without delay.
NOTE 1 Studies have shown that CTC detection is possible in EDTA-collected venous whole blood within 4 h
after blood draw from patients with different tumour types [10–15].
NOTE 2 There are also alternatives to conventional blood collection-based CTC enrichments. These systems
allow for in vivo and ex vivo CTC sampling from larger blood volumes [16] [17].
5.1.3 Venous whole blood specimen collection from the donor/patient and stabilization
procedures
1) The identity of the person collecting the specimen and the date and time of blood collection
according to EN ISO 15189:2012, 5.4.4.3, f) shall be documented.
2) For the labelling/tagging (sample/specimen identification) of the blood collection tube a routine
procedure (EN ISO 15189:2012, 5.4.4.3, e) or a procedure with additional information (e.g. 2D-
barcode) shall be used.
3) Standard venipuncture techniques can be used. Steps for preventing possible backflow into the
donor's/patient’s body can be required. The manufacturer’s instructions for using the blood
collection tubes shall be followed. A blood collection set and needle holder can be required when
using CTC stabilizer containing tubes. In this case, the instructions of the collection set and needle
holder manufacturer shall be followed.
NOTE 1 The integrity of CTC can be influenced by inadequate venous whole blood collection procedures.
4) Blood collection tubes shall be filled in accordance to the manufacturer’s instructions and attention
shall be drawn to the correct positioning of the collection tube during the blood draw as well as the
required blood volume.
5) The blood collection tube manufacturer’s instructions for mixing or inverting the tube immediately
after blood collection shall be followed. Mixing or inverting the blood collection tube shall be done
gently.
NOTE 2 If the additives in the blood collection tubes are not homogenously mixed with the specimen, the CTCs
can be impacted, which can affect the validity and reliability of the examination results.
6) Any tampering with and/or additions to the specimen shall be documented.
5.1.4 Information on the specimen and storage requirements at the blood collection facility
5.1.4.1 General
As CTCs can change significantly after blood collection (see 5.1.2) and can thereby affect the validity and
reliability of the examination result, the documentation regarding the specimen shall include the date
and time of blood collection.
The storage conditions (i.e. storage duration and temperature) shall be documented.
The temporary storage duration in the blood collection facility contributes to the total duration for
storage.
5.1.4.2 Using blood collection tubes with stabilizers
As for storage, the specimens collected in commercial blood collection tubes with CTC stabilizers, the
blood collection tube manufacturer’s instructions on storage conditions shall be followed (e.g.
temperature and storage duration).
Where the CTC enrichment system manufacturer’s instructions and/or the isolation system
manufacturer’s instructions are available and more stringent, the most stringent shall be applied.
Where the CTC examination manufacturer’s instructions are available, these shall be followed. The
storage conditions (i.e. temperature and storage duration) shall be documented.
5.1.4.3 Using blood collection tubes without stabilizers
Where the CTC examination manufacturer's instructions on storage conditions are available, these shall
be followed.
Where the CTC examination manufacturer's instructions are not available, but the CTC enrichment
system manufacturer’s instructions and/or the isolation system manufacturer’s instructions are
available, the most stringent (e.g. shortest storage duration) shall be followed.
The storage conditions (i.e. temperature and storage duration) shall be documented.
Where there are no requirements on the storage conditions available, the specimens should be
processed without delay to maximize the CTC recovery and nucleic acid yield and quality. The storage
conditions (i.e. temperature and storage duration) shall be verified and documented.
5.2 Transport requirements
5.2.1 General
The required transport conditions shall be followed and documented including any deviations
therefrom.
Temperature monitoring should be applied in a suitable manner (e.g. temperature tracking).
5.2.2 Using blood collection tubes with stabilizers
Where using blood collection tubes with CTC stabilizers, the dedicated tube manufacturer’s instructions
on transport conditions shall be followed (e.g. duration and temperature).
Where the CTC enrichment system manufacturer’s instructions and/or the isolation system
manufacturer’s instructions are available and more stringent, the most stringent shall be applied.
Where the CTC examination manufacturer’s instructions are available, these shall be followed.
5.2.3 Using blood collection tubes without stabilizers
Where CTC examination manufacturer's instructions on transport conditions are available, these shall
be followed.
Where CTC examination manufacturer's instructions are not available, but the CTC enrichment system
manufacturer’s instructions and/or the isolation system manufacturer’s instructions are available, the
most stringent (e.g. transport duration) shall be followed.
Where there are no instructions on transport conditions available, the specimen should be transported
at room temperature without delay. The transport conditions (i.e. duration and temperature) shall be
verified and documented
The specimen shall not be frozen and precaution shall be taken to avoid the specimen from being
shaken vigorously.
For additional information on transport, see also EN ISO 15189:2012, 5.4.5.
The transport duration to the laboratory contributes to the total duration for storage.
6 Inside the laboratory
6.1 Specimen reception
The specimen reception date and time shall be documented as well as the name of the person receiving
the specimen. Non-conformities of labelling/tagging, transport conditions and blood volume differences
to specifications, leaking/broken tubes etc., shall be documented.
Where there are non-conformities in labelling/tagging, transport conditions, overall storage and
transport duration or blood volume that could affect the validity and reliability of the examination
result, a new specimen should be obtained.
The correct identity of the specimen shall be checked. This should include the clinical information (see
5.1.1 and 5.1.3) of the specimen, hospital admission number, and/or donor/patient ID, name of the
donor/patient, date of birth of the donor/patient.
6.2 Storage requirements for the venous whole blood specimen
The storage temperature and time interval between specimen receipt and sample processing for CTC
enrichment shall be documented. Storage temperature and total storage duration shall not exceed
specifications identified in 5.1.4 and 5.2.
The specimen total storage duration shall include the duration for storage at the blood collection facility
(5.1.4), for transportation to the laboratory (5.2) and for further storage at the laboratory or other
institutions.
The stability of CTCs can vary between different blood donors/patients, and different blood storage
conditions. The specified maximum storage duration according to 5.1.4 shall not be exceeded. If there
are no specifications available, the maximum storage duration shall be verified and generally kept to a
minimum.
6.3 Enrichment of CTCs
6.3.1 General
CTC enrichment is achieved based on the physical (e.g. cell size, cell deformability) and/or the biological
properties (e.g. presence of specific epitopes) of these cells [1].
The choice of the CTC enrichment method is dependent on the examination requirements. CTC
enrichment procedures are either commercially available or can be laboratory developed. If a dedicated
CTC enrichment system is required by the examination manufacturer, this shall be used.
The CTC stabilizer in a blood collection tube can also be effective during the CTC enrichment depending
on the chemical characteristics of the stabilizer. If the CTC stabilizer used in the blood collection tube is
not effective anymore during CTC enrichment, an additional stabilizer should be added for the CTC
enrichment procedure.
6.3.2 Using a commercial CTC enrichment system
Where using a commercial CTC enrichment system, its manufacturer's instructions shall be followed.
This can include the usage of a specific blood collection tube (see 5.1.2).
The composition of a stabilizer in the blood collection tube can require a modification of the CTC
enrichment procedure. Where the blood collection tube manufacturer has therefore modified the CTC
enrichment system manufacturer's instructions fit-for-purpose and performed a verification and, if
required a validation, the blood collection tube manufacturer's instructions shall be followed instead.
Where the CTC examination manufacturer provides instructions for CTC enrichment, these shall be
followed. Where these are not available, but CTC isolation system manufacturer’s instructions for CTC
enrichment are available, these shall be followed.
6.3.3 Using laboratory’s own CTC enrichment protocols
If a commercial CTC enrichment system is part of a complete verified and validated diagnostic workflow
and not used in accordance to its manufacturer’s instructions, but a laboratory developed procedure is
used, in order to maintain the manufacturer's performance characteristics and the intended use, it shall
be verified for the same specifications and validated for the same intended use. The instructions for this
procedure shall be documented and followed.
If a commercial CTC enrichment system is intended to be a module of a self-composed diagnostic
workflow and not used in accordance to its manufacturer’s instructions, or an own laboratory
developed CTC enrichment procedure is used, design input specifications and intended use defined by
the user shall be verified and validated according to applicable requirements, such as international,
national or regional standards, regulations and/or guidelines. The instructions for this procedure shall
be documented and followed.
6.4 Quality of enriched CTCs
For demonstrating the presence of CTCs in the enriched sample, the examination and/or the CTC
enrichment and/or the CTC isolation manufacturer’s instructions can require an image analysis of the
enriched CTCs, e.g. by haematoxylin and eosin staining (see CEN/TS 17390-3:2020, Molecular in vitro
diagnostic examinations — Specifications for pre-examination processes for Circulating Tumor Cells
(CTCs) in venous whole blood — Part 3: Preparations for analytical CTC staining) or surface protein
staining.
Staining can impact the CTC DNA examination. Compatibility of the CTC staining procedure with the
DNA examination shall therefore be verified during the development of the examination.
The CTC enrichment performance should be tested in a proficiency test program.
NOTE Recently new software for more precise CTC identification criteria has been developed, allowing for
unambiguous identification of cells to be isolated [18].
6.5 Storage of enriched CTCs
Enriched CTCs can optionally be stored prior to CTC isolation (6.6) or DNA isolation (6.8).
For storage, the examination manufacturer's instructions shall be followed, where available.
Where the CTC examination manufacturer's instructions are not available, but the CTC enrichment
system manufacturer’s instructions and/or the CTC isolation system manufacturer’s instructions are
available, the most stringent shall be followed.
Where neither of these are available, the blood collection tube manufacturer's instructions shall be
followed.
Where there are no instructions available, enriched CTCs should be processed to CTC isolation (6.6) or
DNA isolation (6.8) without delay. If this is not possible or preferable, the storage duration shall be
specified and verified for the intended examination.
6.6 Isolation of the CTCs
6.6.1 General
CTC isolation implies the separation of CTCs from all other blood components, usually after CTC
enrichment. CTC isolation is mainly based on physical principles; by e.g. dielectrophoresis,
micromanipulation.
The choice of the CTC isolation system is dependent on the compatibility with the used CTC enrichment
system and with the examination requirements. It shall be ensured that the CTC enrichment system and
the CTC isolation system are compatible.
If a CTC isolation system is specified by the examination manufacturer, this shall be used. Where CTC
examination manufacturer's instructions are not available, but the CTC enrichment system
manufacturer’s instructions and/or the isolation system manufacturer’s instructions are available, the
most stringent shall be followed.
The correct identification of CTCs for isolation is a key requirement. Where the examination
manufacturer’s instructions for the identification of CTCs are available, these shall be followed.
Where the examination manufacturer’s instructions for the identification of CTCs are not available, the
CTC isolation system manufacturer’s instructions shall be followed.
Where neither the examination manufacturer’s instructions nor the CTC isolation system
manufacturer’s instructions are available, the CTC enrichment system manufacturer's instructions shall
be followed.
Where there are no instructions available, the laboratory shall define and verify own criteria for the
identification of CTCs.
6.6.2 Using a commercial CTC isolation system
Where using a commercial CTC isolation system, the manufacturer's instructions shall be followed.
Where the CTC enrichment system manufacturer has modified the CTC isolation system manufacturer's
instructions fit-for-purpose and performed verification and validation, the CTC enrichment system
manufacturer's instructions shall be followed instead.
Where the examination system manufacturer has modified the CTC isolation system manufacturer's
instructions or the CTC enrichment system manufacturer’s instructions, the examination system
manufacturer's instructions shall be followed instead
6.6.3 Using the laboratory’s own CTC isolation procedure
If a commercial CTC isolation system is part of a complete verified and validated diagnostic workflow
and not used in accordance to its manufacturer’s instructions, but a laboratory developed procedure is
used, in order to maintain the manufacturer's performance characteristics and the intended use, it shall
be verified for the same requirements and validated for the same intended use. In this case, the
instructions for this alternative shall be written and followed.
If a commercial CTC isolation system is intended to be a module of a self-composed diagnostic workflow
and not used in accordance to its manufacturer’s instructions, or an own laboratory developed CTC
isolation procedure is used, design input specifications and intended use defined by the user should be
verified and validated according to applicable international, national or regional standards, regulations
and/or guidelines.
The instructions for this procedure shall be documented and followed.
6.7 Processing of isolated CTCs
Isolated single CTCs and pooled isolated CTCs are usually not processed for DNA extraction due to the
very low quantity of DNA. Instead, the isolated CTCs are introduced to the examination directly or only
a lysis step is performed prior to the examination, depending on the examination design.
Where the examination manufacturer's instructions on processing isolated CTCs are available (e.g. lysis
step, direct introduction to the examination or DNA isolation), these shall be followed. Where the
examination manufacturer specifies a DNA isolation kit, this shall be used. Where there are no
examination manufacturer's instructions available, but the CTC isolation manufacturer specifies a
dedicated DNA isolation kit, this shall be used.
Where no examination manufacturer's instructions are available, the laboratory shall define and verify
how to process the isolated CTCs (e.g. lysis step, direct introduction to the examination or DNA
isolation) depending on the examination design. DNA isolation can be preferable for isolated CTC pools
containing higher cell numbers.
It is recommended that CTC processing is done without delay. If this is not possible or preferable, the
storage duration shall be verified.
6.8 Isolation of DNA from an enriched CTC sample
6.8.1 General
To avoid a cross contamination with amplified material, the isolation of the DNA should not be
performed in the same area as the amplification steps of the examination process, unless a closed
system is used.
6.8.2 Using a commercial DNA isolation kit
Where using a commercial DNA isolation kit, the manufacturer's instructions shall be followed.
Where the examination manufacturer specifies
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